The present invention relates to a process for preparing aqueous solutions of acrylamide polymers which are used to improve the constitution of soils.
In many parts of the world, large tracts of land remain sterile and arid because they do not absorb nor retain rain or irrigation water. This lack of moisture is an obstacle to the growth of plants and therefore these soils are easily eroded by wind and by rain.
Furthermore, when a valuable soil is cultivated for a number of years with no respect for its structure, the agricultural yield will decrease with time. This yield reduction results from intensive mechanical agricultural work with heavy farm machinery which compress the soil and damage its structure.
It has already been proposed to apply bituminous emulsion or polymeric compositions as continuous coatings or in strips in order to retain moisture in the soil and to prevent or restrict soil movements. However, this method does not modify the physical properties of the soil whose structure is not improved. In fact, this method is only applicable to previously seeded soils whose nature is such that they easily retain moisture.
Polymerizable mixtures containing acrylamide monomer as a main constituent, a cross-linking agent and a polymerization catalyst have been suggested as soil-stabilizing agents. These compositions are injected into the soils where they are polymerized. However, these mixtures are used to solidify and harden soft foundations in engineering work and in construction. They are not suitable for improving the structure of poor soils or for stabilizing the structure of good soils for agricultural purposes.
Other processes comprise the use of polyacrylamide solutions, instead of acrylamide solutions. The soils are treated with an aqueous solution of polyacrylamide and with an aqueous solution of cross-linking agent. The polymer is thus transformed into a hydrogel forming aggregates with the soil particles. However, the effectiveness of this method varies and depends on some factors; the results are not always reproducible.